/*
 * Copyright (C) 2007 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.HashMap;
import java.util.Map;

import javax.annotation.Nullable;

import com.google.common.annotations.GwtCompatible;

/**
 * A {@link BiMap} backed by two {@link HashMap} instances. This implementation
 * allows null keys and values. A {@code HashBiMap} and its inverse are both
 * serializable.
 * 
 * @author Mike Bostock
 * @since 2010.01.04 <b>stable</b> (imported from Google Collections Library)
 */
@GwtCompatible
public final class HashBiMap<K, V> extends AbstractBiMap<K, V> {

    /**
     * Returns a new, empty {@code HashBiMap} with the default initial capacity
     * (16).
     */
    public static <K, V> HashBiMap<K, V> create() {
        return new HashBiMap<K, V>();
    }

    /**
     * Constructs a new, empty bimap with the specified expected size.
     * 
     * @param expectedSize
     *            the expected number of entries
     * @throws IllegalArgumentException
     *             if the specified expected size is negative
     */
    public static <K, V> HashBiMap<K, V> create(int expectedSize) {
        return new HashBiMap<K, V>(expectedSize);
    }

    /**
     * Constructs a new bimap containing initial values from {@code map}. The
     * bimap is created with an initial capacity sufficient to hold the mappings
     * in the specified map.
     */
    public static <K, V> HashBiMap<K, V> create(
            Map<? extends K, ? extends V> map) {
        HashBiMap<K, V> bimap = create(map.size());
        bimap.putAll(map);
        return bimap;
    }

    private HashBiMap() {
        super(new HashMap<K, V>(), new HashMap<V, K>());
    }

    private HashBiMap(int expectedSize) {
        super(new HashMap<K, V>(Maps.capacity(expectedSize)),
                new HashMap<V, K>(Maps.capacity(expectedSize)));
    }

    // Override these two methods to show that keys and values may be null

    @Override
    public V put(@Nullable K key, @Nullable V value) {
        return super.put(key, value);
    }

    @Override
    public V forcePut(@Nullable K key, @Nullable V value) {
        return super.forcePut(key, value);
    }

    /**
     * @serialData the number of entries, first key, first value, second key,
     *             second value, and so on.
     */
    private void writeObject(ObjectOutputStream stream) throws IOException {
        stream.defaultWriteObject();
        Serialization.writeMap(this, stream);
    }

    private void readObject(ObjectInputStream stream) throws IOException,
            ClassNotFoundException {
        stream.defaultReadObject();
        int size = Serialization.readCount(stream);
        setDelegates(Maps.<K, V> newHashMapWithExpectedSize(size),
                Maps.<V, K> newHashMapWithExpectedSize(size));
        Serialization.populateMap(this, stream, size);
    }

    private static final long serialVersionUID = 0;
}
